What makes you say that they're invalid? Put these fonts in a folder called "Document Fonts" in the same folder as your InDesign file. Close the ID file and re-open. Are the fonts still missing? Also, what OS are you running?

OK, it looks like you're running windows. My guess is that Mac fonts were supplied with the job. You cannot use Mac TrueType or PostScript fonts on a Windows computer. OpenType fonts however are cross-platform. Your choices are:

Obtain the Windows versions of these fonts and replace them in the document.

Purchase a tool such as TransType to convert the fonts to the Windows version

Replace the fonts with a font that you have. (Not recommended as it will change the appearance of the document).

Extensis Suitcase is simply a font manager. Another way to activate and de-activate fonts on your system. It's used in design/production environments to save time by not having to quit applications when you activate/de-activate fonts. It's not going to help your situation.

Your problem, is a pretty simple one. You need the fonts loaded on your machine in order to properly view/print/export the InDesign document. Without them, the file will not look as intended. How you get rid of the missing fonts is to load fonts on your machine that will work. I think you'll find that if you price out purchasing the Windows versions of the font, it will be much more expensive than TransType Pro. An alternative is to choose Type > Find Font, and replace the missing font with a font that you have loaded on your system. Again, it will not look the same as the original document, but the fonts will no longer be missing. Hope that helps.

Let's take a step backwards for a second. Dan, what is the end goal for this document? If you need to make changes and edits to it, then you need the fonts. If not, can you ask the person who supplied you with the file to generate a PDF of the file? Would that be sufficient?